This invention relates to a method of fabricating a tube container and more specifically to a method of fabricating tube container in which an outer sleeve having a larger diameter and an inner sleeve having a smaller diameter are coaxially arranged so as to contain different kinds or colors of creamy contents separately therein, and wherein both of the creamy contents be pressed out from a discharge opening and mixed with each other when they are consumed.
Such tube containers are disclosed in Japanese Provisional Utility Model Publication No. 188150/1985 and Japanese Utility Model Publication Nos. 11091/1988, 41339/1988 and 41340/1988.
Each of these known tube containers is of a double sleeve structure in which an inner sleeve having an integrally formed neck and shoulder is disposed inside an outer sleeve also having an integrally formed neck and shoulder. There is provided a nozzle piece between the neck of the outer sleeve and that of the inner sleeve for discharging a first creamy content from the inner sleeve and a second creamy content from the outer sleeve as they are mixed therethrough.
Generally, for the fabrication of a tube container comprising a single sleeve having a shoulder and a neck at one end thereof, a sleeve is first shaped by extrusion molding, and then one end portion of the sleeve is placed in a die to form the shoulder and neck by injection molding.
Accordingly, for obtaining the above conventional tube container having the double sleeve structure, it is necessary to form the shoulder and the neck not only for the outer sleeve but also for the inner sleeve by injection molding. This means that the molding procedures required therefor are equivalent to those for forming at least two different sizes of tube containers. Between the so-formed neck of the inner sleeve and that of the outer sleeve is disposed a nozzle piece for discharging the first and second creamy contents as they are mixed therethrough. However, in the conventional tube container, since the bottom end of the nozzle piece is adapted to be fitted in the neck formed in the inner sleeve, the diameter of the discharge passage communicating with the first creamy content to be provided along the central portion of the nozzle piece in the inner sleeve is very much smaller than that of the neck of the inner sleeve, thus increasing the resistance discharge of the first creamy content. On the other hand, when the diameter of the neck formed in the inner sleeve is enlarged so as to enlarge the diameter of the discharge passage along the central portion of the nozzle piece, the space defined between the nozzle piece and the neck of the outer sleeve becomes narrow, thus increasing the resistance to discharge of the second cream content.
Also, in the conventional tube container having a double sleeve structure of thermoplastic resin, the inner sleeve and the outer sleeve have substantially the same length, so that the lower ends of these inner and outer sleeves are terminated at substantially the same level. When the lower ends of the inner and outer sleeves are sealed, they are pinched and compressed in the radial direction by a heat sealing bar, for example, for welding of the thermoplastic resin. In such a case, since the inner sleeve has a smaller diameter than the outer sleeve, opposite external side portions of the outer sleeve are welded into two layers, while the middle part therebetween is welded into four layers. This results in a difference of thickness when welding the lower ends of both sleeves. Because of such difference of thickness, it has been difficult to homogeneously seal the lower ends of the sleeves by a pair of sealing bars. Although there are some proposals which intend to compensate such difference of thickness, no satisfactory solution yet has been provided.